<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Hello World!</title>
    <style>
        html, body {
            width: 100%; height: 100%; margin: 0; padding: 0; overflow: hidden;
        }
        #cesiumContainer,#cesiumContainer2{
            width: 50%; height: 100%; margin: 0; padding: 0; overflow: hidden;
        }
    </style>
</head>
<body>
<div id="cesiumContainer"></div>
<div id="cesiumContainer2"></div>

<script>
    var viewer = new Cesium.Viewer('cesiumContainer');
    var viewwer2 =  new Cesium.Viewer('cesiumContainer2');
</script>
</body>
</html>